Using functional diversity as an indicator of restoration success of a cut-over bog

A trait-based approach was used to evaluate the restoration success of a moss layer transfer technique on the herbaceous community of a cut-over bog. In order to understand the herbaceous dynamics following restoration, the bog was monitored prior to restoration and biannually over ten subsequent years, in two initial drainage conditions (dry peat fields and wet ditches), and compared to seven undisturbed bogs. Herbaceous community found prior to and in the early stage after restoration were characterized by species associated to mesic soil conditions with a fen-like pH, ruderal or wetland species, species with mycorrhiza or exotic species. These species did not persist in the latter stage after restoration and were replaced by species that are carnivorous, are associated to variable water availability and show mostly sexual reproduction. The extent of changes in traits composition of the herbaceous community between the early and latter stages after restoration showed the importance of multiple-year monitoring to evaluate restoration projects. The trait composition found in the latter stage after restoration appeared to converge toward the reference ecosystem where the community was characterized by species with large seeds, associated to humid soil conditions and a forest or peatland habitat. Lower trait diversity was found in the latter stage after restoration than in the reference ecosystem, especially in peat fields. In addition, species and functional diversity pattern varied with the initial drainage conditions, decreasing in peat fields while remaining stable in ditches. This suggests that different initial topography for restoration might help increase species and functional diversity of a managed ecosystem. Finally, our results outline measures to improve the moss layer transfer technique: sowing herbaceous species with large seeds in the latter stage after restoration, applying the restoration technique as soon as exploitation has terminated or removing all vegetation (including seeds and rhizomes) from the site to be restored. (C) 2012 Elsevier B.V. All rights reserved.